The present invention, in some embodiments thereof, relates to optics and, more particularly, but not exclusively, to a method and system for transmitting light via light filamentation.
When electromagnetic radiation is focused to a point to ionize a fluid, the resulting plasma diffracts the light and dispersion occurs. However, high-power pico- and femto-second-duration laser pulses have been found to propagate over large distances, while ionizing the fluid in their path. This phenomenon is referred to in the literature as light filamentation.
Filamentation has been observed using a variety of gases, such as nitrogen, helium, and air. Filamentation has also been demonstrated in liquids and solids, although with shorter propagation lengths. The wavelengths for filamentation have been observed ranging from infrared to ultraviolet.
A light filament is typically formed when a femtosecond pulse with peak intensity above the critical power for collapse is propagating in a transparent medium [A. Braun, G. Korn, X. Liu, D. Du, J. Squier, and G. Mourou, Opt. Lett. 20, 73 (1995)]. In air, the diameter of a light filament is approximately 100 μm and it can propagate over distances much longer than the Rayleigh length [Rodriguez et al., Phys. Rev. E 69, 036607 (2004); Kasparian et al., Science, 301, 61 (2003); Méchain et al., Appl. Phys. B: Lasers Opt. B79, 379 (2004); Mills et al., Opt. Lett., 38, 25 (2013); Chin et al, Appl. Phys. B74, 67-76 (2002)].
Quantum rotational wave packets have been observed in atmospheric air on filamentary propagation of femtosecond laser pulses [Varma et al., Phys. Rev. Lett. 101, 205001 (2008)]. This study reports that a probe filament that is by several tens of picoseconds or less with respect to a pump filament can be sucked into the pump filament's molecular quantum wake and be either trapped or destroyed by it.
Recently, it was discovered that on a millisecond timescale, a laser pulse leaves a density hole that reduces the index of refraction at the center of the beam as a result of heating [Cheng et al., Optics Express, 21 4740 (2013)]. This phenomenon has a defocusing effect on a next pulse in a sequence of pulses.